If you're going to drive a vehicle so lengthy you need to plug back-to-back parking meters, so tall you'll make a running leap to hop inside, so powerful it gets just 14 miles to the gallon, it's nice to have a fueling option other than gas.

That's the scenario Ram is offering with its 2500 CNG, a heavy-duty pickup that lets drivers keep on truckin' using either $2-per-gallon compressed natural gas or $3.50-per-gallon 87 octane. The 2500 CNG first went on sale for fleet buyers earlier this year and is now available to retail customers, Ram announced in October.

Chrysler is the last of the Detroit manufacturers to offer a CNG pickup. But the first bi-fuel vehicle from the company's truck brand underscores the segment's shift toward alternative fuels in a way that's distinctly American. The 2500 CNG pairs one of the most meat-and-potatoes machines on the road with an energy source largely birthed from U.S. soil.

CNG is a fossil fuel sourced from the methane in oil and natural gas wells, as well as shale deposits and landfill biogas. More than 85 percent of the stuff is produced domestically. The Ram's CNG tanks carry a gasoline equivalent of 18.2 gallons – enough fuel to travel 255 miles. And if the tanks run out, there's a gasoline backup that kicks in seamlessly using the same 383-horsepower Hemi revered for its ability to haul entire herds.

Being an urban mom, the only livestock I keep at my eighth-of-an-acre L.A. spread are domesticated rodents. And while I needed to re-up my supply of timothy hay for my son's guinea pig collection, driving the Ram 2500 to do so felt like bringing a pitchfork to dinner.

Whatever projects I needed to accomplish in the week I drove the 2500 didn't exactly push the limits of its 1,580-pound payload or the nearly four tons it can tow. But it did come in handy hauling 14 years' worth of newspaper clips from the office of my former employer, and doing so with a lot less pain at the pump.

Like an increasing array of vehicles, the 2500 is available with mix-and-match drive trains. It can be had in gasoline, diesel or the CNG bi-fuel version, which, in the SLT trim, cost $40,165, $48,460 and $51,165, respectively.

Yes, you read that right. The bi-fuel version costs about 25 percent more. For that kind of cash, buyers might be inclined to stick with the gas-powered 2500 and use the $11,000 savings to buy a brand-new Nissan Versa for the missus.

At 14 mpg for both fuels, it would cost $2,205 to run the truck on CNG for a year vs. $3,581 for gas at current prices. Financially, it could take more than five years for the CNG version to pay off, presuming the U.S. average of 13,476 miles of annual driving.

Environmentally, however, the savings are immediate – and monumental. Depending on the source, burned CNG generates between 31 percent and 89 percent fewer greenhouse gas emissions than gasoline, according to the California Air Resources Board. And compared with regular gas, CNG generates 40 percent fewer carbon dioxide emissions, 87 percent fewer oxides of nitrogen and maybe even a pat on the back from your neighborhood greenie.

What allows the 2500 to run on gas as well as CNG using the same 5.7-liter V8 is its fuel delivery system. There are separate fuel rails for the gas and CNG. Firing up the truck, the engine uses regular gas, but it immediately switches to natural gas as long as both tanks are fueled.

The 2500 CNG has been in development since Chrysler went belly up and was bailed out by the federal government, which, as crises tend to do, got the good folks in Detroit thinking differently.

It was in 2009 when a natural gas trade group approached the company about building a truck that would support the droves of manly men dispatched to drill for the clear elixir flowing up from the ground at many points west of the Atlantic – a time that synced up with Chrysler's partial purchase by Fiat, which makes 80 percent of all CNG vehicles in Europe and helped engineer the Ram CNG.

The 2500 CNG is Ram's most recent foray into alternative drive-train territory. Some of its heavy-duty trucks are also compatible with biodiesel.

Chrysler's Ram 2500 CNG is the only bi-fuel pickup on the U.S. market that is engineered and built by the manufacturer. Ford has been offering CNG bi-fuel conversions of its F-Series super-duty trucks since 2009. Unlike the CNG Ram, which is built at the same Mexican plant as other Ram 2500s, Ford's conversions aren't done at the factory but, rather, at Ford-approved Qualified Vehicle Modifiers for an equally wallet draining $9,500 to $11,000 a pop. Earlier this year, General Motors began offering bi-fuel conversions of its Chevrolet Silverado and GMC Sierra extended-cab heavy-duty pickup trucks that are up fit through GM suppliers for a $11,000 premium.

A Dodge Ram 2500 HD CNG (Compressed Natural Gas) cruises along Ortega Highway in San Juan Capistrano. H. LORREN AU JR., THE ORANGE COUNTY REGISTER
The Dodge Ram 2500 HD CNG is one of the biggest vehicles on the road. H. LORREN AU JR., THE ORANGE COUNTY REGISTER
Compressed Natural Gas generates 40 percent less carbon dioxide emissions and 87 percent fewer oxides of nitrogen than a similar sized gas-powered vehicle. H. LORREN AU JR., THE ORANGE COUNTY REGISTER
Language stamped on the exterior of a new Dodge Ram 2500 HD CNG identifies it as a bi-fuel vehicle that uses compressed natural gas. Besides running on natural gas, it can also use unleaded gasoline. H. LORREN AU JR., THE ORANGE COUNTY REGISTER
Opening a Dodge Ram 2500 HD CNG truck's bed-mounted container permits access to two 4.6-cubic-foot compressed natural gas tanks. H. LORREN AU JR., THE ORANGE COUNTY REGISTER
Among other locations sprinkled throughout the Southern California area, compressed natural gas (CNG) can be purchased at this South Coast Air Quality Management District station in Diamond Bar. H. LORREN AU JR., THE ORANGE COUNTY REGISTER
Compressed Natural Gas is sold in units of GGEs, or gasoline gallon equivalents. The price to fill a vehicle with compressed natural gas is, at this location, about half the cost of fueling with unleaded gasoline. This is a pump located at the South Coast Air Quality Management District station in Diamond Bar. H. LORREN AU JR., THE ORANGE COUNTY REGISTER

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